An object and problem of the present invention is based on offering secure migration ways for fish and other organisms living in water past power stations, dam constructions and other water plants.
The present invention is based on using an Archimedes screw, which is driven in rotation and thereby is adapted for lifting liquid and organisms living in the liquid from the volume of water being situated lower to the volume of water being situated higher. By its function as a transporter for water, the present invention can also operate as a pump adapted for lifting water from the volume of water situated lower to the volume of water situated higher.
Archimedes screws have been used for these purposes. In the Dutch patent NL 1029915 an example is shown of using a motor-powered screw for lifting water and fish over a dam construction. Another example of a motor-powered screw in an apparatus for catching and transporting up living fish from a basin is disclosed in the U.S. Pat. No. 4,217,718. A third example of using a motor-powered screw for transporting up fish is disclosed in the international publication WO 95/15079.
Common for all these known solutions is that they are based on using a single, motor-powered screw adapted for one-way transport of water and fish.
A pumping unit in which twin Archimedes screws are used is known from the Japanese publication JP 57088277 A. In this pump an inner screw is mounted co-axially in relation to an outer screw, wherein the screws are provided with a drive means and by means of a power distribution device individually are driven in rotation for enabling regulation and adaption due to requirements of the lifting capacity of the pump.
It is also noted that it is known from the power industry to use an Archimedes screw for power production by means of providing the screw such that it is driven in rotation of a water-flow from a volume of water situated higher to a volume of water situated lower, wherein the screw is coupled to a generator for production of electricity.